Patent GB-1417802-A (GB)
Title: Lead frame and process facilitating the manufacture of electric devices having semiconductor chips placed in a face-to-face relation
IPC: H01L21/60
Filed: 1973-02-08
Abstract: 1417802 Semi-conductor devices; component assemblies MOTOROLA Inc 8 Feb 1973 [15 March 1972] 6279/73 Headings H1K and H1R A semi-conductor device comprises a pair of semi-conductor dies, e.g. a light emitting diode and a light responsive transistor or SCR, juxtaposed facing so that the latter receives light from the former to selectively control, e.g. its resistance; conductively mounted on lead frames, separated by transparent material, and encapsulated with protruding connection members. An elongate lead frame portion 10 (Fig. 1) divided into segments 12, 14, 16 is etched stamped or machined from a metallic strip of, e.g. Ni, and each segment comprises, e.g. end joining bands 18, 20, parallel side bars 22, 24, and lead spacing members 25, 27; the segments enclosing a central area 30. Fingers extending into area 30 have end portions 34, 44 of which the control portions bear mounting areas 36, 48 for supporting semi-conductor chips, e.g. light emitting diode and, e.g. phototransistor; the fingers being respectively connected over members 25, 27 and lead portions 54, 55 to bands 18, 20. Interconnecting members 51 adapted to dovetail fit apertures 50 are integral with side bars 22, 24, and indexing apertures 56 of bands 18, 20 align the frame during automated manufacture. The inner ends of the fingers (Fig. 2, not shown) are offset to lie in a plane parallel to and displaced from that of the lead frame, and the surfaces are plated with Au. A Si chip providing a light emitting diode is mounted on area 36, and a Si chip providing a phototransistor is mounted on area 48 by an automatic die bonder in a line production machine engaging indexing apertures 56, and a wire bonder connects Au wires 62 from flanking fingers to electrodes of the chips by thermocompression welding. Thereafter member 25 is sheared along lines 64 to separate the frame into two portions 70, 72 (Fig. 3) and the lower half 72 is turned 180 degrees (Fig. 4) and offered to the upper half 70 so that projections 51 interlock apertures 50, and corresponding pairs of chips 60, 61 are juxtaposed face to face. Corresponding laterally spaced projections and apertures also interlock to define lead frame 90 with segments 92, 94, 96 (Fig. 4). The offset ends of the mounting fingers lie in separate planes to hold the semi-conductor chips 60, 61 in opposition, and side joining bars 78, 80 and lead spacing members 25, 27 lie in a distinct plane parallel thereto (Fig. 5). Transparent material is inserted between the chips (Fig. 6, not shown) and may form part of the encapsulant plastic, which is applied in a transfer mould; the indexing apertures being positioned to engage members of the mould faces which enclose the side joining bars and lead spacing members. An e.g. thermosetting phenolic or silicon plastic is forced into each mould which contains a respective semiconductor pair and the relevant connections to form an enclosing body, e.g. 100 (Fig. 4). After encapsulation, members 25, 27 are trimmed off by shearing along lines 102 to separate the encapsulated devices and their leads from frame 90, and the leads are bent over at 90 degrees for insertion into a socket; being arranged in parallel rows one on each side (Fig. 7, not shown). In modifications (Fig. 8 to 10, not shown) alternative structures accommodate dual semiconductor chips with more than three electrodes and connecting leads, or triple such chips of which one is eventually located in sandwich between the others.